A typical component in most burglar alarm security systems is a magnetically operated proximity switch. These switches are comprised of two portions; a small magnetic contact reed switch and an external permanent magnet. When the magnetic contact reed switch portion is held in close proximity along side the permanent magnet portion, the reed switch contacts are maintained in a closed position allowing electrical current to flow due to the completion of an electrical circuit. When the permanent magnet portion is moved away from the magnetic contact reed switch, the contacts open breaking the electrical circuit. By mounting the magnetically operated proximity switch on a door or window, the opening of such can be detected and register by a burglar alarm security system. There are two types of magnetically operated proximity switches. One is a surface mounted type. The other is a recessed mounted type. The surface mounted type is the easier to install of the two because it attaches to the door or window surface with conventional fastening means while both portions of the recessed mounted type require countersank holes often 3/4 to 1 inch in depth. The surface mounted magnetically operated proximity switch used primarily on windows is installed by attaching the magnetic contact reed switch portion to the stationary window jam and the permanent magnet portion to the movable window sash. The proximity switch is installed with both portions in close proximity when the window is in the closed position. Therefore when the window is opened, the contacts of the switch are opened and the open circuit condition is detected by the burglar alarm security system.
The foregoing burglar alarm security system operates satisfactorily until the need for one or more of the windows to remain partially open. Once this situation occurs, the burglar alarm security system cannot be activated because the alarm will sound immediately when the open circuit condition due to the open window(s) is detected.
A possible way of addressing the problem would be to reposition the permanent magnet portion of the magnetically operated proximity switch such that the permanent magnet and the magnetic reed switch portions are in close proximity when the window is in the opened position. However, this will not suffice when the converse situation arises requiring the same window(s) to remain closed while the burglar alarm security system is operational.
Another approach would be to install two permanent magnet portions on the same window sash. The first positioned to be in close proximity to the magnetic reed switch portion when the window is in the closed position and the second positioned to be in close proximity to magnetic reed switch portion when the window is in the partially opened position. Cost wise, this is unacceptable since the magnetic reed s witch and external permanent magnet portions are sold in pairs. Two permanent magnet portions would be needed per window leaving one unused magnetic reed switch per window.
Some burglar alarm security systems provide a mechanism which allows the selective by-passing of all or part (i.e. particular window(s)) of the closed detection circuit. The window(s) could then remain open, however, no intrusion detection would be present for that particular window(s).
No prior art apparatus or method exists utilizing magnetically operated proximity switches in a burglar alarm security system which provides a practical and economic means to enable such a system to supply intrusion detection while windows of the system are interchangeably either in an opened or closed position.